Azetidine 2-carboxylic acid (Aze) is consumed by humans and can be misincorporated in place of proline (Pro) in myelin basic protein (MBP). In systemically treated mice Aze induced distinct oligodendroglial (OL) alterations mimicking those in multiple sclerosis (MS) patient normal-appearing white matter. Here, Aze induced an unfolded protein response (UPR), cytoplasmic MBP aggregation, apoptosis and tumor necrosis factor secretion in the human OL lineage MO13.3 cell line. These alterations were counteracted by equimolar Pro suggesting that they are due to Aze substitution for Pro in OL proteins. Gene set enrichment analysis demonstrated extensive Aze-induced alterations of cell cycle, cytoskeletal, organelle, transport, developmental, inflammation-associated and myelination pathways that are altered in OL in MS patients and in toxin and inflammatory MS animal models. These data provide mechanistic support for the hypothesis that Aze protein misincorporation during early life myelinogenesis might over time result in a progressive UPR culminating in a pro-inflammatory/immunomodulatory phenotype, intracytoplasmic MBP aggregation, accelerated senescence and apoptosis in OL. This could occur prior to and independent of an external immune stimulus such as a viral infection. Aze-induced pathological alterations might enhance subsequent antiviral and autoimmune responses and contribute to MS susceptibility, lesion pathogenesis, remyelination failure, neurodegeneration and clinical progression.

Interleukin 23 receptor (IL-23R) signaling is critical for the generation of pro-inflammatory CD4+ IL-17-producing T helper cells (Th17) that can drive autoimmune tissue inflammation, but the underlying mechanisms are not clear. We integrated phosphoproteomic and transcriptomic data downstream of IL-23R and IL-12 receptor (IL-12R), which share a common subunit, to identify mechanisms engaged specifically by IL-23. We identified chromodomain helicase DNA-binding protein 1 (CHD1), an epigenetic regulator, and the glucocorticoid receptor (GR), a transcription factor (TF), as mediators of IL-23R signaling. IL-23R activation promoted CHD1 interaction with TF STAT3 and co-binding at the TF RORγt locus to enforce a pro-inflammatory Th17 state. Conversely, IL-23R signaling altered phosphorylation of the GR, thereby preventing its activation and nuclear translocation, ultimately impairing GR-driven inhibition of pro-inflammatory Th17 gene programs. Our findings uncover two mechanisms by which IL-23 promotes a pro-inflammatory Th17 cell state, offering potential therapeutic targets for treating Th17-driven autoimmune tissue inflammation and restoring homeostasis.

T helper 17 (Th17) cells are heterogeneous: homeostatic Th17 (Th17Hom) cells maintain tissue homeostasis, and pro-inflammatory Th17 (Th17Inf) cells drive autoimmune inflammation. IL-23 drives Th17Inf, but the signals that maintain Th17Hom remain unclear. Here, we found that differential glucocorticoid (GC) production downstream of CYP11A1, a critical enzyme for steroidogenesis, distinguished Th17Hom cells from Th17Inf cells. Although TCR signaling opened the Cyp11a1 locus, TGF-β1 and IL-6, key cytokines for Th17Hom cell differentiation, maintained and amplified Cyp11a1. Th17Hom cell-derived GC signaled through the glucocorticoid receptor (GR), which was higher in Th17Hom cells compared with Th17Inf cells, thereby forming a circuit that maintained the homeostatic state. Integration of multi-omics data from CYP11A1- and GR-deficient Th17Hom cells revealed a gene network underlying this circuit. TGF-β1, a key node in the network, restored GC sensing to Th17Inf. We thus identify a GC signaling circuit that maintains Th17 homeostasis with implications for treating Th17-mediated autoimmunity.

BACKGROUND AND OBJECTIVES:Aquaporin (AQP)-4 (AQP4)-seropositive neuromyelitis optica (NMO) frequently coexists with rheumatologic autoimmune conditions, including Sjögren syndrome and systemic lupus erythematosus, 2 conditions that share a common HLA-DRB1 (HLA-DRB1*03:01) association with NMO. AQP4 is a member of a family of ubiquitously expressed water channels. Its immunodominant pathogenic T-cell epitope, which binds MHC II with exceptionally high affinity, is homologous to sequences in other AQPs, including AQP5, a candidate target autoantigen in Sjögren syndrome. Thus, we hypothesized that self-antigen molecular mimicry exists between AQPs and contributes to autoimmunity. METHODS:Previously, we examined binding of AQP4 T-cell epitopes to MHC II (I-Ab) by biochemical assays; we now evaluate interaction of I-Ab and AQPs by molecular modeling. T cells from mice immunized with the immunodominant AQP4 epitope or its homologous AQP5 sequence were examined for proliferation and cross-recognition between AQPs. T-cell receptor (TCR) engagement of individual T cells with AQP-MHC II complexes was examined using AQP4 and AQP5 peptide/MHC II tetramers. The pathogenic potential of AQP4-primed and AQP5-primed T cells was examined by T-cell adoptive transfer into naïve mice. RESULTS:The immunodominant AQP4 T-cell epitope was predicted to make optimal contacts within the pockets of the MHC II antigen-binding cleft. Like AQP4, the corresponding homologous AQP5 amino acid sequence was predicted to bind MHC II, albeit with modest affinity. In a reciprocal manner, T cells were detected that proliferated to both AQP4 and AQP5. Multi-tetramer analysis of individual T cells demonstrated that the same TCR could engage both AQP4 and AQP5. T cells from mice immunized with AQP4 or AQP5 caused paralysis and CNS inflammation in recipient mice, but not in AQP4-deficient mice, demonstrating that AQP4 expression is obligately required in this model of aquaporin CNS autoimmunity. DISCUSSION:T cells can express TCRs that recognize multiple AQPs. Autoimmunity can be initiated through molecular mimicry between distinct self-antigens such as AQP4 and AQP5 that are expressed in separate organs. These findings suggest that T-cell self-antigen mimicry may contribute to coexistence of NMO with other autoimmune conditions, such as Sjögren syndrome.

Mapping the brain's fiber network is crucial for understanding its function and malfunction, but resolving nerve trajectories over large fields of view is challenging. Here, we show that computational scattered light imaging (ComSLI) can map fiber networks in histology independent of sample preparation, also in formalin-fixed paraffin-embedded (FFPE) tissues including whole human brain sections. We showcase this method in new and archived, animal and human brain sections, for different sample preparations (in paraffin, deparaffinized, various stains, unstained fresh-frozen). We convert microscopic orientations to microstructure-informed fiber orientation distributions (μFODs). Adapting tractography tools from diffusion magnetic resonance imaging (dMRI), we trace axonal trajectories revealing white and gray matter connectivity. These allow us to identify altered microstructure or deficient tracts in demyelinating or neurodegenerating pathology, and to show key advantages over dMRI, polarization microscopy, and structure tensor analysis. Finally, we map fibers in non-brain tissues, including muscle, bone, and blood vessels, unveiling the tissue's function. Our cost-effective, versatile approach enables micron-resolution studies of intricate fiber networks across tissues, species, diseases, and sample preparations, offering new dimensions to neuroscientific and biomedical research.

Glucose metabolism is a critical regulator of T cell function, largely thought to support their activation and effector differentiation. Here, we investigate how individual glycolytic reactions determine the pathogenicity of T helper 17 (Th17) cells using Compass, an algorithm we previously developed for inferring metabolic states from single-cell RNA sequencing. Surprisingly, Compass predicted that the metabolic shunt between 3-phosphoglycerate (3PG) and 2-phosphoglycerate (2PG) is inversely correlated with pathogenicity in Th17 cells. Indeed, perturbation of phosphoglycerate mutase (PGAM), the enzyme catalyzing 3PG to 2PG conversion, induces a pathogenic gene expression program by suppressing a gene module associated with the least pathogenic state of Th17 cells. Finally, PGAM inhibition in Th17 cells exacerbates neuroinflammation in the adoptive transfer model of experimental autoimmune encephalomyelitis, consistently with PGAM promoting the non-pathogenic phenotype of Th17 cells. Overall, our study identifies PGAM, contrary to other glycolytic enzymes, as a negative regulator of pathogenic Th17 cell differentiation.

Myocarditis is one of the major causes of heart failure in children and young adults and can lead to dilated cardiomyopathy. Lymphocytic myocarditis could result from autoreactive CD4+ and CD8+ T cells, but defining antigen specificity in disease pathogenesis is challenging. To address this issue, we generated T cell receptor (TCR) transgenic (Tg) C57BL/6J mice specific to cardiac myosin heavy chain (Myhc)-α 334–352 and found that Myhc-α-specific TCRs were expressed in both CD4+ and CD8+ T cells. To investigate if the phenotype is more pronounced in a myocarditis-susceptible genetic background, we backcrossed with A/J mice. At the fourth generation of backcrossing, we observed that Tg T cells from naïve mice responded to Myhc-α 334–352, as evaluated by proliferation assay and carboxyfluorescein succinimidyl ester staining. The T cell responses included significant production of mainly pro-inflammatory cytokines, namely interferon (IFN)-γ, interleukin-17, and granulocyte macrophage-colony stimulating factor. While the naïve Tg mice had isolated myocardial lesions, immunization with Myhc-α 334–352 led to mild myocarditis, suggesting that further backcrossing to increase the percentage of A/J genome close to 99.99% might show a more severe disease phenotype. Further investigations led us to note that CD4+ T cells displayed the phenotype of cytotoxic T cells (CTLs) akin to those of conventional CD8+ CTLs, as determined by the expression of CD107a, IFN-γ, granzyme B natural killer cell receptor (NKG)2A, NKG2D, cytotoxic and regulatory T cell molecules, and eomesodermin. Taken together, the transgenic system described in this report may be a helpful tool to distinguish the roles of cytotoxic cardiac antigen-specific CD4+ T cells vs. those of CD8+ T cells in the pathogenesis of myocarditis.

T helper (Th) 17 cells encompass a spectrum of cell states, including cells that maintain homeostatic tissue functions and pro-inflammatory cells that can drive autoimmune tissue damage. Identifying regulators that determine Th17 cell states can identify ways to control tissue inflammation and restore homeostasis. Here, we found that interleukin (IL)-23, a cytokine critical for inducing pro-inflammatory Th17 cells, decreased transcription factor T cell factor 1 (TCF1) expression. Conditional deletion of TCF1 in mature T cells increased the pro-inflammatory potential of Th17 cells, even in the absence of IL-23 receptor signaling, and conferred pro-inflammatory potential to homeostatic Th17 cells. Conversely, sustained TCF1 expression decreased pro-inflammatory Th17 potential. Mechanistically, TCF1 bound to RORγt, thereby interfering with its pro-inflammatory functions, and orchestrated a regulatory network that determined Th17 cell state. Our findings identify TCF1 as a major determinant of Th17 cell state and provide important insight for the development of therapies for Th17-driven inflammatory diseases.

Co-inhibitory and checkpoint molecules suppress T cell function in the tumor microenvironment, thereby rendering T cells dysfunctional. Although immune checkpoint blockade is a successful treatment option for multiple human cancers, severe autoimmune-like adverse effects can limit its application. Here, we show that the gene encoding peptidoglycan recognition protein 1 (PGLYRP1) is highly coexpressed with genes encoding co-inhibitory molecules, indicating that it might be a promising target for cancer immunotherapy. Genetic deletion of Pglyrp1 in mice led to decreased tumor growth and an increased activation/effector phenotype in CD8+ T cells, suggesting an inhibitory function of PGLYRP1 in CD8+ T cells. Surprisingly, genetic deletion of Pglyrp1 protected against the development of experimental autoimmune encephalomyelitis, a model of autoimmune disease in the central nervous system. PGLYRP1-deficient myeloid cells had a defect in antigen presentation and T cell activation, indicating that PGLYRP1 might function as a proinflammatory molecule in myeloid cells during autoimmunity. These results highlight PGLYRP1 as a promising target for immunotherapy that, when targeted, elicits a potent antitumor immune response while protecting against some forms of tissue inflammation and autoimmunity.

Aquaporin-4 (AQP4)-specific Th17 cells are thought to have a central role in neuromyelitis optica (NMO) pathogenesis. When modeling NMO, only AQP4-reactive Th17 cells from AQP4-deficient (AQP4 −/− ), but not wild-type (WT) mice, caused CNS autoimmunity in recipient WT mice, indicating that a tightly regulated mechanism normally ensures tolerance to AQP4. Here, we found that pathogenic AQP4 T cell epitopes bind MHC II with exceptionally high affinity. Examination of T cell receptor (TCR) α/β usage revealed that AQP4-specific T cells from AQP4 −/− mice employed a distinct TCR repertoire and exhibited clonal expansion. Selective thymic AQP4 deficiency did not fully restore AQP4-reactive T cells, demonstrating that thymic negative selection alone did not account for AQP4-specific tolerance in WT mice. Indeed, AQP4-specific Th17 cells caused paralysis in recipient WT or B cell-deficient mice, which was followed by complete recovery that was associated with apoptosis of donor T cells. However, donor AQP4-reactive T cells survived and caused persistent paralysis in recipient mice deficient in both T and B cells or mice lacking T cells only. Thus, AQP4 CNS autoimmunity was limited by T cell–dependent deletion of AQP4-reactive T cells. In contrast, myelin oligodendrocyte glycoprotein (MOG)-specific T cells survived and caused sustained disease in WT mice. These findings underscore the importance of peripheral T cell deletional tolerance to AQP4, which may be relevant to understanding the balance of AQP4-reactive T cells in health and in NMO. T cell tolerance to AQP4, expressed in multiple tissues, is distinct from tolerance to MOG, an autoantigen restricted in its expression.

Enteroviruses, which include Coxsackieviruses, are a common cause of virus infections in humans, and multiple serotypes of the group B Coxsackievirus (CVB) can induce similar diseases. No vaccines are currently available to prevent CVB infections because developing serotype-specific vaccines is not practical. Thus, developing a vaccine that induces protective immune responses for multiple serotypes is desired. In that direction, we created a live-attenuated CVB3 vaccine virus, designated mutant (Mt)10, that offers protection against myocarditis and pancreatitis induced by CVB3 and CVB4 in disease-susceptible A/J mice. Here, we report that the Mt10 vaccine protected against CVB4-triggered type 1 diabetes (T1D) in non-obese diabetic (NOD) mice but the expected subsequent development of spontaneous T1D in these genetically predisposed NOD mice was not altered. We noted that Mt10 vaccine induced significant amounts of neutralizing antibodies, predominantly of the IgG2c isotype, and the virus was not detected in vaccine-challenged animals. Furthermore, monitoring blood glucose levels—and to a lesser extent, insulin antibodies—was found to be helpful in predicting vaccine responses. Taken together, our data suggest that the monovalent Mt10 vaccine has the potential to prevent infections caused by multiple CVB serotypes, as we have demonstrated in various pre-clinical models.

Dendritic cells (DCs) sense environmental cues and adopt either an immune-stimulatory or regulatory phenotype, thereby fine-tuning immune responses. Identifying endogenous regulators that determine DC function can thus inform the development of therapeutic strategies for modulating the immune response in different disease contexts. Tim-3 plays an important role in regulating immune responses by inhibiting the activation status and the T cell priming ability of DC in the setting of cancer. Bat3 is an adaptor protein that binds to the tail of Tim-3; therefore, we studied its role in regulating the functional status of DCs. In murine models of autoimmunity (experimental autoimmune encephalomyelitis) and cancer (MC38-OVA-implanted tumor), lack of Bat3 expression in DCs alters the T cell compartment-it decreases TH1, TH17 and cytotoxic effector cells, increases regulatory T cells, and exhausted CD8+ tumor-infiltrating lymphocytes, resulting in the attenuation of autoimmunity and acceleration of tumor growth. We found that Bat3 expression levels were differentially regulated by activating versus inhibitory stimuli in DCs, indicating a role for Bat3 in the functional calibration of DC phenotypes. Mechanistically, loss of Bat3 in DCs led to hyperactive unfolded protein response and redirected acetyl-coenzyme A to increase cell intrinsic steroidogenesis. The enhanced steroidogenesis in Bat3-deficient DC suppressed T cell response in a paracrine manner. Our findings identified Bat3 as an endogenous regulator of DC function, which has implications for DC-based immunotherapies.

Background and ObjectivesAnti-CD20 monoclonal antibody (mAb) B-cell depletion is a remarkably successful multiple sclerosis (MS) treatment. Chimeric antigen receptor (CAR)-T cells, which target antigens in a non-major histocompatibility complex (MHC)-restricted manner, can penetrate tissues more thoroughly than mAbs. However, a previous study indicated that anti-CD19 CAR-T cells can paradoxically exacerbate experimental autoimmune encephalomyelitis (EAE) disease. We tested anti-CD19 CAR-T cells in a B-cell-dependent EAE model that is responsive to anti-CD20 B-cell depletion similar to the clinical benefit of anti-CD20 mAb treatment in MS.MethodsAnti-CD19 CAR-T cells or control cells that overexpressed green fluorescent protein were transferred into C57BL/6 mice pretreated with cyclophosphamide (Cy). Mice were immunized with recombinant human (rh) myelin oligodendrocyte protein (MOG), which causes EAE in a B-cell-dependent manner. Mice were evaluated for B-cell depletion, clinical and histologic signs of EAE, and immune modulation.ResultsClinical scores and lymphocyte infiltration were reduced in mice treated with either anti-CD19 CAR-T cells with Cy or control cells with Cy, but not with Cy alone. B-cell depletion was observed in peripheral lymphoid tissue and in the CNS of mice treated with anti-CD19 CAR-T cells with Cy pretreatment. Th1 or Th17 populations did not differ in anti-CD19 CAR-T cell, control cell-treated animals, or Cy alone.DiscussionIn contrast to previous data showing that anti-CD19 CAR-T cell treatment exacerbated EAE, we observed that anti-CD19 CAR-T cells ameliorated EAE. In addition, anti-CD19 CAR-T cells thoroughly depleted B cells in peripheral tissues and in the CNS. However, the clinical benefit occurred independently of antigen specificity or B-cell depletion.

BACKGROUND:Unresolved inflammation in multiple sclerosis (MS) is associated with progressive demyelination and symptom worsening. In the brain, both inflammation and resolution pathways are mediated by free lipid mediators (i.e., oxylipins) that can be derived from the enzymatic hydrolysis of esterified oxylipins . It is not known whether disturbances in the turnover of free lipid mediators from esterified pools exist in postmortem brain of MS patients. We hypothesized that resolution pathways are impaired in MS patients because of disturbances in the turnover of free pro-resolving lipid mediators from esterified lipids. The objective was to characterize free and esterified oxylipins in postmortem prefrontal cortex of MS and unaffected control participants.METHODS:Oxylipins in free, neutral lipid and phospholipid pools were extracted from prefrontal cortex of 10 MS participants and 5 unaffected controls, separated by solid phase extraction columns, and quantified by ultra-high-pressure liquid chromatography-tandem mass spectrometry. Significant differences between the control and MS groups were determined by an unpaired t-test with Benjamini and Hochberg False Discovery Rate correction (10%) applied to oxylipins within each lipid pool.RESULTS:The concentration of 7 esterified pro-resolving fatty acid epoxides within neutral lipids were significantly higher by 126%-285% in postmortem prefrontal cortex of MS compared to control participants. The concentration of esterified linoleic acid-derived 9(10)-epoxy-octadecenoic acid, a pro-inflammatory epoxide, was higher by 206% in MS compared to controls. No significant changes were observed in free or phospholipid-bound oxylipins.CONCLUSION:In MS, several pro-resolving lipid mediators are trapped within prefrontal cortex neutral lipids, potentially limiting their supply and availability in the free bioactive form. This may explain why inflammation resolution is impaired in MS patients.

The naturally occurring imino acid azetidine-2-carboxylic acid (Aze) is consumed by humans and can be misincorporated in place of proline in myelin basic protein (MBP) in vitro. To determine Aze effects on the mammalian CNS in vivo, adult CD1 mice were given Aze orally or intraperitoneally. Clinical signs reminiscent of MBP-mutant mice occurred with 600 mg/kg Aze exposure. Aze induced oligodendrocyte (OL) nucleomegaly and nucleoplasm clearing, dilated endoplasmic reticulum, cytoplasmic vacuolation, abnormal mitochondria, and Aze dose-dependent apoptosis. Immunohistochemistry demonstrated myelin blistering and nuclear translocation of unfolded protein response (UPR)/proinflammatory molecules (ATF3, ATF4, ATF6, eIF2 alpha, GADD153, NF kappa B, PERK, XBP1), MHC I expression, and MBP cytoplasmic aggregation in OL. There were scattered microglial nodules in CNS white matter (WM); other CNS cells appeared unaffected. Mice given Aze in utero and postnatally showed more marked effects than their dams. These OL, myelin, and microglial alterations are found in normal-appearing WM (NAWM) in multiple sclerosis (MS) patients. Thus, Aze induces a distinct oligodendrogliopathy in mice that recapitulates MS NAWM pathology without leukocyte infiltration. Because myelin proteins are relatively stable throughout life, we hypothesize that Aze misincorporation in myelin proteins during myelinogenesis in humans results in a progressive UPR that may be a primary process in MS pathogenesis.

Objective Evaluate chimeric antigen receptor (CAR)-T cell mediated B cell depletion in experimental autoimmune encephalomyelitis (EAE). Background CAR-T cells are autologous T cells expressing a non-MHC target antigen specific receptor. We tested whether anti-CD19 CAR-T cells, which more thoroughly deplete human B cell populations than monoclonal antibodies (mAbs), recapitulated the beneficial effects of B cell depletion in EAE. Design/Methods Anti-CD19 CAR-T cells or control T cells that overexpressed green fluorescent protein were transferred into female wild-type C57BL/6 mice that had been pretreated with cyclophosphamide. EAE was induced by immunization with either recombinant human (rh) myelin oligodendrocyte protein (MOG) (B cell-dependent) or MOG peptide (p) 35-55 (B cell-independent). Mice were evaluated daily for clinical signs of EAE and weekly for peripheral B and T cell counts. B cell levels, T cell immune modulation and histology were assessed at peak disease and at termination. Results In rhMOG-induced EAE, clinical scores and histologic lymphocyte infiltration were reduced in mice treated with cyclophosphamide and either anti-CD19 CAR-T cells or control T cells. B cell depletion was observed in peripheral lymphoid tissue and in the central nervous system (CNS) of mice treated with anti-CD19 CAR T cells, similar to effects of anti-CD20 mAbs. There was no difference in T cell modulation including Th1 or Th17 populations, but there was a trend towards increase in Treg populations in the periphery and CNS in the anti-CD19 CAR-T cell and control T cell treated animals. Clinical scores and histology did not differ among treatment groups in p35-55-induced disease. Conclusions Anti-CD19 CAR-T cells thoroughly deplete B cells peripherally and within the CNS. Treatment also results in less severe rhMOG-induced disease, but it was independent of B cell depletion. Our results are consistent with human data indicating that anti-CD19 CAR-T cells deplete B cells across compartments, suggesting that they may hold promise for progressive MS.